全文获取类型
收费全文 | 800篇 |
免费 | 38篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 278篇 |
金属工艺 | 22篇 |
机械仪表 | 7篇 |
建筑科学 | 25篇 |
能源动力 | 20篇 |
轻工业 | 98篇 |
水利工程 | 9篇 |
石油天然气 | 3篇 |
无线电 | 51篇 |
一般工业技术 | 98篇 |
冶金工业 | 142篇 |
原子能技术 | 8篇 |
自动化技术 | 70篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 51篇 |
2021年 | 62篇 |
2020年 | 24篇 |
2019年 | 27篇 |
2018年 | 22篇 |
2017年 | 23篇 |
2016年 | 25篇 |
2015年 | 16篇 |
2014年 | 26篇 |
2013年 | 54篇 |
2012年 | 30篇 |
2011年 | 52篇 |
2010年 | 26篇 |
2009年 | 40篇 |
2008年 | 22篇 |
2007年 | 29篇 |
2006年 | 21篇 |
2005年 | 22篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 55篇 |
1997年 | 29篇 |
1996年 | 27篇 |
1995年 | 19篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1970年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有839条查询结果,搜索用时 0 毫秒
31.
Morrone Isabella; Declercq Christelle; Novella Jean-Luc; Besche Chrystel 《Canadian Metallurgical Quarterly》2010,25(3):697
The inhibitory deficit hypothesis has often been cited as a possible explanation for cognitive changes related to age. The aim of this study was to develop a new procedure for evaluating effortful inhibition on the basis of the comprehension of metaphors. Our experiment was carried out on younger and older adults, in whom we also measured inhibitory capacity, working memory, and processing speed. The results show that older participants required a longer time and made more frequent errors in rejecting metaphors versus literally false statements. The interference effect was predicted by the psychometric tests designed to evaluate inhibition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
32.
This paper presents a two-level state estimation methodology intended to integrate in a simple and efficient manner the results provided by local estimators, handling measurements at the substation level, within the framework of existing EMS. This leads to a paradigm in which raw measurements are locally pre-processed by a linear estimator, in such a way that only a manageable subset of measurements is handled at the second level, significantly reducing the communication bandwidth. Simulation results show that, even when the two steps are centrally carried out, the proposed approach is computationally more efficient than the conventional one, particularly with highly redundant measurement sets. 相似文献
33.
34.
Isabella Panfoli Daniela Calzia Silvia Ravera Paolo Bianchini Alberto Diaspro 《Microscopy research and technique》2010,73(12):1086-1090
We describe a procedure for the labeling of membranous vesicular purified subcellular fractions, to image them, typically by confocal laser scanning microscopy. Being intracellular organelles, these fractions, once purified cannot be attached to glass slides as for cells. Fractions are labeled “in batch” without prior embedding or freezing. Each labeling step performed by passages of resuspension/centrifugation is followed by washings. Then samples are dispersed on the glass slides. Mammalian retinal rod outer segment disks, intact brain stem myelin vesicles, and brain synaptosomes were chosen, as these subcellular fractions can be purified by well established procedures. These fractions were immunolabeled with specific antibodies. Moreover, by the earlier procedure, we show that the mitochondrial vital membrane potential probe MitoTracker Deep Red 633 stains myelin vesicles and rod disks before fixation, consistently with our previous reports of a respiring capacity of these membranes. Therefore, the technique seems adequate to become an instrument to study the structure and the function of these and other subcellular fractions. Microsc. Res. Tech. 73:1086–1090, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
35.
We propose a robust procedure based on the regularized phase-tracking (RPT) technique to demodulate squared-grating deflectograms. The use of squared gratings, already reported, lets us multiplex the information of the deflections in two orthogonal directions in a single image, thus avoiding the necessity of rotating the gratings. The good noise-rejection characteristics of the RPT technique are improved by use of a quasi-Newton optimization algorithm and a quality-map-based algorithm for the crystal-growing process. 相似文献
36.
VG Nicoletti EA Tendi C Lalicata S Reale A Costa RF Villa N Ragusa AM Giuffrida Stella 《Canadian Metallurgical Quarterly》1995,20(12):1465-1470
The contents of subunits I, II/III, and IV of cytochrome c oxidase and of subunits alpha, beta and gamma of FoF1 ATP synthase in inner mitochondrial membrane proteins purified from cerebral cortex of rat at 2, 6, 12, 18, 24, and 26 months of age were analyzed by western blot. Age-related changes in the content of subunits, either of mitochondrial or nuclear origin, were observed. All the cytochrome c oxidase (COX) subunits examined showed an age-related increase from 2-month-old rats up to 24 months with a decrease at the oldest age (26 months). The same pattern of age-dependent changes was observed for gamma ATP synthase, while the alpha and beta subunits increased progressively up to 26 months. 相似文献
37.
38.
MG Daidone E Benini B Valentinis G Tomasic G Bolis A Villa R Silvestrini 《Canadian Metallurgical Quarterly》1996,(8):1388-1393
The aim of this study was to investigate biological heterogeneity between primary and metastatic ovarian cancer lesions from individual patients as a means of elucidating steps in clinical progression. Cancer tissue from 61 untreated patients with ovarian surface epithelial-stromal tumours was examined. p53 expression detected immunocytochemically by the PAb1801 antibody, DNA content evaluated by flow cytometry, and cell proliferation evaluated as the [3H]thymidine labelling index were investigated in primary tumours and corresponding synchronous metastases. The frequency of p53 positivity was similar in primary (62%) and metastatic (66%) sites, with an agreement between the two lesions from the same patient in 97% of the cases. Similarly, aneuploidy frequency (80%) and DNA indices were superimposable in primary and metastatic lesions from the same patient, with a 94% agreement. The frequency of aneuploidy was higher in p53-positive than in p53-negative lesions. An overall poor agreement (rs = 0.44) was observed for proliferative activity of primary and metastatic lesions, due to a heterogeneous profile in omental with respect to primary tumours, which was mainly evident in p53-positive cancers. Conversely, cell proliferation of peritoneal, abdominal and pelvic lesions was qualitatively similar to that of the primary tumour in 88% of patients. 相似文献
39.
The expression of the beta-amyloid precursor protein (APP), which plays a key role in the development of Alzheimer's disease, is regulated by a variety of cellular mediators in a cell-dependent manner. In the present study, we present evidence that thyroid hormones negatively regulate the expression of the APP gene in neuroblastoma cells. Transient transfection studies using plasmids that contain progressive deletions of the 5' region of the gene demonstrate that triiodothyronine (T3), the more active form of the thyroid hormones, represses APP promoter activity by a mechanism that requires binding of the nuclear T3 receptor (TR) to a specific sequence located in the first exon. The unliganded receptor increases promoter activity, and T3 reverses that activity to basal levels. The repressive effect of T3 does not exhibit TR isoform specificity, and it is equally mediated by TRalpha and TRbeta. Gel mobility shift assays using in vitro synthesized nuclear receptors and nuclear extracts led to the identification of a negative thyroid hormone response element, at nucleotide position +80/+96, that preferentially binds heterodimers of TR with the retinoid X receptor. Insertion of sequences containing this element confers negative regulation by T3 to a heterologous TK promoter, thus indicating the functionality of the element. 相似文献
40.
RE Miguel LL Villa AC Cordeiro JC Prado JS Sobrinho LP Kowalski 《Canadian Metallurgical Quarterly》1998,176(5):428-429
BACKGROUND: The main purpose of this study was to determine the prevalence of human papillomavirus (HPV) infection in patients with head and neck carcinomas from Brazil. MATERIALS AND METHODS: Forty-five patients with head and neck squamous cell carcinoma were included in the study, from 1995 to 1996. Forty-two were male and 3 female, with age ranging from 32 to 82 years (median 61). Five patients (11%) did not have previous history of use of tobacco and 38 (90.5%) were heavy smokers. Tumor sites were pyriform sinus, 10; tongue, 11 (oral, 6; base, 5); larynx, 7; floor of mouth, 3; tonsil, 6; retromolar area, 3; inferior gingiva 2; buccal mucosa, 2; and maxillary sinus in 1 patient. Twenty-five were stage IV, 17 stage III, and 3 stage II. RESULTS: The presence of HPV DNA was detected in 5 of 45 patients (11%), all of them with HPV 16. Two patients had HPV DNA in normal mucosa and tumor tissue, 1 patient had HPV DNA only in the normal mucosa and tumor tissue, 1 patient had HPV DNA only in the normal mucosa, and 2 patients were positive for HPV DNA in tumor tissue. Four patients were male and 1 was female; 2 patients were nonsmokers. Three patients had tonsil carcinoma, 1 patient had a tongue carcinoma, and 1 patient had a pyriform sinus cancer. CONCLUSIONS: The role of chemical carcinogens seems to be more important in the genesis of head and neck cancer than is HPV infection. The presence of HPV DNA in 5 of 45 patients stimulates further investigation to determine the role of HPV as a risk factor for head and neck carcinoma. 相似文献